The World on the Day You Were Born
The real sky over your city that night, the moon, the #1 song, the headlines and the strangers born with you — on a certificate of arrival.
In short: pick your birth date (and, if you like, your city and time). In about a second you see the night sky that was over you, the moon phase, the song at number one in the US that week, what happened on that date, famous people born on it, the world population and roughly how many babies arrived the same day (for most birth years, between 250,000 and 380,000). All of it is free, with no sign-up.
What you get for your birthday
| On the page | Where it comes from |
|---|---|
| Star chart of your sky | Calculated for your city and time from the Yale Bright Star catalogue (via d3-celestial) and the IAU constellation figures |
| Moon phase and % lit | Sun and Moon positions, low-precision astronomical series (Meeus) |
| US number one song | Billboard Hot 100 weekly #1, every chart since 4 Aug 1958 |
| Births that day, world population | UN World Population Prospects 2024 (1950+), HYDE / Our World in Data before 1950 |
| Weather | Open-Meteo historical reanalysis (ERA5), 1940 onward, when you add a city |
| Events and famous birthdays | Wikipedia “On this day” (CC BY-SA 4.0) |
How to read your star chart
The circle is the whole sky above you, horizon at the edge and the point straight overhead in the middle. North is at the top and east is on the left — that is how the sky looks when you lie down with your head to the north. Gold lines join the stars of each constellation; the small disc is the Moon, drawn in its phase, if it was above the horizon. Stars visible from your city but below the horizon at that hour are not shown.
Born on this day: your birthday twins
“Born on your birthday” lists people with a Wikipedia article born on your date, those from your birth year first. Roughly 250,000–380,000 people share your exact birth date and year; a few of them become famous enough to be on the list.
Questions
What was the world like when I was born?
Enter your birthday above. You get the moon phase and the real night sky over your city, the Billboard Hot 100 number one that week, the world population, how many babies were born the same day, the weather (for 1940 onward when you add a city), events from that date in history, and famous people who share your birthday.
What happened on the day I was born?
The "What happened" list shows events on your exact date from Wikipedia's On this day, with events from your birth year highlighted first and nearby years after. Most days have a handful of recorded events; the list is the same one Wikipedia uses for its front page.
What song was number 1 when I was born?
We look up the Billboard Hot 100 chart dated on or just before your birthday — every week since the chart began on 4 August 1958. For birthdays before that, there was no Hot 100 yet.
What was the moon phase on my birthday?
The moon tile shows the phase name, how much of the moon was lit and its age in days, calculated from the positions of the Sun and Moon at midnight (or at your birth time) in your city's time zone. It is accurate to well under a day.
Is the star chart real?
Yes. It is the sky above your city at your birth time, worked out from about 2,000 stars brighter than magnitude 5.2 and the 88 constellation figures, with north at the top and east on the left, as if you were lying on your back looking up. Without a city we show the sky over the Royal Observatory, Greenwich.
What is a certificate of arrival?
A keepsake that records when and under which sky someone arrived: date, place, the star chart, the moon, the number one song and how many babies were born that day. The preview here is free to share; the HD print edition (no watermark) is a one-time purchase.
Is this like Born Here (bornhere.app)?
Similar idea, different approach. Here the star chart of your actual sky, the headlines and the famous birthdays are free, there is no email step and no animation to sit through, and the result is instant. Born Here tells the story in chapters and sells the rest of them as a pass.
How many babies were born on the same day as me?
We divide the UN World Population Prospects estimate of births in your birth year by 365.25. In recent decades that is roughly 360,000–380,000 babies a day; in 1950 it was about 250,000.